Spring-pressed arrangement for transformer and choke coil windings



March 1965 H. SCHMID ETAL SPRING-PRESSED ARRANGEMENT FOR TRANSFORMER AND CHOKE con. wmnmcs 2 Sheets-Sheet 1 Filed Feb. 14, 1963 m M .0 PP T0 .WE N V i F mmww o lh QT 4 L5} HM J QE H W W 2 Sheet-Sheet 2 H. SCHMID ETAL SPRING-PRESSED ARRANGEMENT FOR TRANSFORMER AND CHOKE COIL WINDINGS F O A I a m M arr March 2, 1965 Filed Feb.

Hams SQAgYEF Q fign gelbert wa genblchler P ,4 x 1 United States Patent "ice 3,172,064 SPRING-PRESSED ARRANGEMENT FOR TRANS- FORMER AND CHOKE COIL WTNDINGS Hans Schmid, Wettingen, Aargau, and Engelbert Wagerihichler, Wettingen, Switzerland, assignors to Alrtiengesellschaft Brown, Eoveri & Cie., Baden, Switzerland, a joint-stock company Filed Feb. 14, 1963, Ser. No. 258,560 Claims priority, application Switzerland, Feb. 28, 1962,

4 Claims. (c1. ass-197 This invention relates to an elastic pressing device for transformer and choke windings having pressing elements located between yoke end plates and pressing rings of the winding.

It is known that under the stress of short-circuit currents, transformer windings become deformed in the axial direction. For this reason, pressing devices have been proposed which are intended to prevent loosening and hence, the danger of destruction of the windings. Rigid compression has proved not to be suflicient, as it is no longer operative as the winding settles. A known pressing device where plate spring bodies are present between pairs of supporting pressing plates is so designed that the spring bodies lying between the pressing plates are prestressed before the device is installed. The pressing plates are screwed together and inserted as a rigid unit between the yoke and the supporting blocks of the winding, and thereafter the initial stress is released. The disadvantage of thi construction is that a relatively large space for the winding as so-called end distance is lost, as the upper pressing plate engages from below the yoke by resting against it through wedges. The pressing pressure is transmitted to the winding by the lower pressing plate over supporting blocks so that an intended different distribution of the pressing pressure along the winding circumference is thereby not possible. Such a readjustment, however, is definitely desired in those cases where the winding settles unevenly.

This is remedied by the new arrangement. The invention proposes that the pressing elements be designed individually elastic and displaceably arranged in guide tracks, in such manner that, in the zone of the yoke end plates, distributed as desired over the circumference of the particular winding, they are connected therewith at several points through pressing rings.

FIGS. 1, 2 and 3 show an arrangement in front elevation, plan and side elevation, respectively, where for three concentric windings, pressing elements are provided at several points of the circumference.

FIG. 4 shows a detail on a larger scale, how the pressing elements are spaced by spacers within the guide tracks; and

FIG. 5 shows as a detail the connection of the guide track with the yoke end plate.

With reference now to FIGS. 1-3, numeral 1 denotes the stepped yoke, which presents at both sides the parallel spaced yoke end plates 2a, 2b. To the latter, at their undersides, guide tracks 3 are connected in longitudinal and transverse directions, which in the transverse direction are supported by gusset plates 4. Pressing elements 5 are displaceably arranged in the guide tracks 3 and are connected through pressing rings 6a, 6b, 60 with the cencentric windings 7a, 7b, '70, respectively. The pressing elements 5 consist is known manner of a stack of plate springs, which is present internally between a pot-like lower part 5a and a similar upper part 5b, the latter being connected through the lock nut pair 50 with the stem 5e, which is threaded. At its upper end the stem 52 has a rectangular guide plate Si by which the pressing element is inserted in the guide tracks 3 (FIG. 5)

3,172,064 Patented Mar. 2, 1965 For fixing the positions of the pressing elements relative to each other, the invention provides bar-shaped spacers 8 in the guide tracks 3. The outermost pressing element is secured by an abutment piece 9, which may be connected with the guide track by screws (FIG. 4). The stem 5e of each pressing element advantageously has a certain pivotability on its axis relative to the pot-like lower part 5a to compensate for any deviations in the desired plane-parallelism between the pressing rings and the yoke end plates, or respectively the guide tracks. This is achieved, for example, in that the contact surface between the lower nut 50 and the upper part 5b is domeshaped. For relatively small transformers, the stem 5e of the pressing element may be designed at the top of its guide plate 5f with a tip 10 (FIG. 5) which during tensioning penetrates into the guide track 3 and thus prevents unintentional displacement, for example, due to vibrations in service.

The mode of :action of the described arrangement is the following: During assembly of the transformer, the pressing elements 5 are first strung up in the guide tracks 3 untensioned, the spacers 8 being inserted as needed. Depending on the type of winding, pressing elements of different pressing force may be used, the guide plates 5f of the stems 5e being of identical design. By displacement of the lock nuts 5c, the desired pressing pressure is then adjusted. If, after the drying out of the transformer or due to the operational stresses, a settling of the winding occurs, each individual pressing element 5 can then be readjusted to the required pressing force at the respective point. This is advantageous in particular in case of a shrinkage unevenly distributed over the circumference of the transformer coil, as well as in the case of manufactur ing and assembly inaccuracies, as the pressing elements are individually adjustable and exchangeable. To make as many points of the winding as possible available for pressing, the guide tracks are so arranged that some of the pressing elements are located in the spaces which are available due to the stepped arrangement of the yoke. In FIG. 2 these are, for example, those pressing elements which form the two rows extending in the longitudinal direction of the transformer. In this way a very small end distance is suflicient, as the yoke may rest directly on the pressing rings on to 60. A further shortening can be achieved by providing the pressing rings with recesses into which the continuous lower yoke portion extends. Such a weakening of the pressing rings is acceptable because pressing elements can be arranged in the direct vicinity of these points.

The new pressing device permits in advantageous manner the construction of transformer and choke windings which are highly resistant to short-circuits. The individual elastic pressing elements are easily exchangeable and, due to their displaceability in the guide tracks are suitably adjustable to the particular winding. Manufacturing and assembly inaccuracies can thus be easily compensated. The end distance can be reduced to a minimum. The resetting of the pressing force is possible 'at any time without disassembly of the transformer, so that also shrinkage of the windings due to operational stresses can easily be countered. The new arrangement thus constitutes an advance with respect to an economical construction for transformer and chokes.

We claim:

1. In :a transformer or choke structure the combination comprising at least one winding arranged as a coil on a magnetic structure including a yoke and parallel spaced end plates therefor, said coil being spaced from said end plates, a pressing ring in said space adjacent said coil, a guide track secured to the underside of each of said end plates and facing said pressing ring, each said guide track being constituted by track sections extending both longitudinally and transversely of said end plates, and individually adjustable elastic pressing elements located in said guide tracks and being displaceable longitudinally in said tracks to positions overlying said pressing ring, said pressing elements each exerting an adjustable force between said guide track and said pressing ring and being distributed as desired over the circumference of said coil in the vicinity of said end plates.

2. The invention as defined in claim 1 wherein said yoke has a stepped configuration and at least some of said pressing elements are located directly beneath stepped portions of the yoke.

3. The invention as defined in claim 1 and which further includes spacer members within said guide track for spacing said pressing elements relative to each other.

4. The invention as defined in claim 1 which comprises a plurality of concentric coils and a plurality of said individually adjustable pressing elements are associated with each such coil.

References Cited in the file of this patent UNITED STATES PATENTS 1,961,761 Hendricks June 5, 1934 2,393,169 Jarmann Jan. 15, 1946 2,817,065 Horelick Dec. 17, 1957 

1. IN A TRANSFORMER OR CHOKE STRUCTURE THE COMBINATION COMPRISING AT LEAST ONE WINDING ARRANGED AS A COIL ON A MAGNETIC STRUCTURE INCLUDING A YOKE AND PARALLEL SPACED END PLATES THEREFOR, SAID COIL BEING SPACED FROM SAID END PLATES, A PRESSING RING IN SAID SPACE ADJACENT SAID COIL, A GUIDE TRACK SECURED TO THE UNDERSIDE OF EACH OF SAID END PLATES AND FACING SAID PRESSING RING, EACH SAID GUIDE TRACK BEING CONSTITUTED BY TRACK SECTIONS EXTENDING BOTH LONGITUDINALLY AND TRANSVERSELY OF SAID END PLATES, AND INDIVIDUALLY ADJUSTABLE ELASTIC PRESSING ELEMENTS LOCATED IN SAID GUIDE TRACKS AND BEING DISPLACEABLE LONGITUDINALLY IN SAID TRACKS TO POSITIONS OVERLYING SAID PRESSING RING, SAID PRESING ELEMENTS EACH EXERTING AN ADJUSTABLE FORCE BETWEEN SAID GUIDE TRACK AND SAID PRESSING RING AND BEING DISTRIBUTED AS DESIRED OVER THE CIRCUMFERENCE OF SAID COIL IN THE VICINITY OF SAID END PLATES. 